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A targeted disruption in connexin40 leads to distinct atrioventricular conduction defects
L M Bevilacqua1, A M Simon, C T Maguire
1Department of Cardiology, Children's Hospital, Harvard Medical School Boston, Massachusetts 02115, USA.
Introduction:
Gap junctions consist of connexin (Cx) proteins that enable electrical coupling of adjacent cells and propagation of action potentials. Cx40 is solely expressed in the atrium and His-Purkinje system. The purpose of this study was to evaluate atrioventricular (AV) conduction in mice with a homozygous deletion of Connexin40 (Cx40(-/-)).
Methods:
Surface ECGs, intracardiac electrophysiology (EP) studies, and ambulatory telemetry were performed in Cx40(-/-) mutant mice and wild-type (WT) controls. Atrioventricular (AV) conduction parameters and arrhythmia inducibility were evaluated using programmed stimulation. Analysis of heart rate variability was based on results of ambulatory monitoring.
Results:
Significant findings included prolonged measures of AV refractoriness and conduction in connexin40-deficient mice, including longer PR, AH, and HV intervals, increased AV refractory periods, and increased AV Wenckebach and 2:1 block cycle lengths. Connexin40-deficient mice also had an increased incidence of inducible ventricular tachycardia, decreased basal heart rates, and increased heart rate variability.
Conclusion:
A homozygous disruption of Cx40 results in prolonged AV conduction parameters due to abnormal electrical coupling in the specialized conduction system, which may also predispose to arrhythmia vulnerability.